Brakes, particularly vehicular brakes, employing a pair of brake shoes lined with frictional braking material and operative to pivot away from each other and brakingly engage a wheel drum in response to rotation of a cam caused by actuating a brake have been used for many years.
Commonly such brake shoes pivot about common or separate fixed posts at one end and have facing open-sided bearing surfaces at the opposite end in which roller followers are placed and which are resiliently biased against an intermediate rotary cam, commonly an "S" shaped cam, that is adapted to spread the brake shoes apart upon rotation of the cam upon actuation of the brake of which illustrative examples are disclosed in U.S. Pat. Nos. 2,710,076 and 4,206,834, the disclosures of which are incorporated herein by reference.
Initially, because the brake shoes are biased towards each other by springs, the trunnions or cylindrical bearing portions of the cam follower roller were simply placed in open-sided bearing surfaces at the end of webs extending from the brake shoe and held in place by being biased against the cover.
Due to alignment problems of the roller follower between the webs and the possibility of dislodging from the brake shoe bearing surfaces due to wear of either the cam or the roller or to contamination or sticking of the brake shoes to the drum while the cam is rotated to the disengaged position or wear of the frictional braking material, a variety of retainers have been devised over the years for retaining the trunnions of the cam follower roller in the open-sided bearing surfaces provided in the brake shoe webs.
An early example of a "U" shaped retainer for holding the rotary cam follower roller in the brake shoe open-sided bearing surfaces is disclosed in U.S. Pat. No. 3,275,103, the disclosure of which is incorporated herein by reference. Although effective to align the rolling surface of the roller between the cam shoe webs, one would have to employ a tool to reach through openings in the webs and bend tabs before the retainer could be removed from the webs.
Another example of a retainer for retaining cam follower rollers in the open-sided brake shoe bearing surfaces is disclosed in U.S. Pat. 3,469,660, the disclosure of which is incorporated herein by reference. Here, however, it is required that holes be made in the end of each roller trunnion and that arms be welded to the webs carrying pins that enter the holes to retain the roller to the open-sided bearing surfaces which is costly and time consuming.
Further examples of brake roller retainers are respectively disclosed in U.S. Pat. Nos. 4,503,953 and 4,624,348, the disclosures of which is incorporated herein by reference. Both provide a "U" shaped retainer having arms which only partially surround the roller trunnions so that the roller trunnions can be removed therefrom in order to remove the retainer from the webs and which diminishes assurance that the roller trunnions will be held in the open-sided bearing surfaces.
None of the above-described retainers provide a simple and economical way of encircling the roller trunnions completely to insure retention and still be able to easily remove the roller and the retainer from the web without having to first remove the roller from the retainer.